1. Field of the Invention
This invention relates to an information processing method whereby a light is applied to a recording medium and information is recorded on the recording medium or the information recorded on the recording medium is reproduced and to an information processing apparatus used for such recording or such reproduction or both.
2. Description of the Prior Art
In recent years, along with the advance of information technology, optical information processing apparatuses in which light is converged on the surface of a recording medium and information is recorded or reproduced have been attracting attention. In such information processing apparatuses, there is generally provided light scanning means for scanning the converged light on the surface of the recording medium. Heretofore, mechanical light deflecting means such as a galvano mirror or the like has been used as such light scanning means, wherein this has suffered from a disadvantage that the scanning speed is low. Therefore, it would occur to mind to use the light deflector utilizing diffraction proposed in U.S. Pat. No. 4,425,02, etc., instead of said mechanical light deflecting means. An example of the information processing apparatus using such a light deflector will hereinafter be described by reference to FIGS. 1A and 1B of the accompanying drawings.
FIG. 1A shows the construction of the information reproducing apparatus according to the prior art. In FIG. 1A, reference numeral 1 designates a thin film type light deflector utilizing the diffraction of light by an elastic surface wave, reference numeral 2 denotes a beam splitter, reference numeral 3 designates an objective lens, reference numeral 4 denotes a condensing lens, reference numeral 5 designates a photodetector, and reference numeral 6 denotes a recording medium. The light deflector 1 is constructed as shown, for example, in FIG. 1B. On a substrate 11, there is formed a waveguide layer 12 having a refractive index higher than that of the substrate 11, and incident light 15 is directed into the waveguide layer 12 through a prism coupler 14. Part of the incident light propagated through the waveguide is diffracted by an elastic surface wave 18 produced from a combtooth-like electrode 13 and becomes a deflected light 16. This deflected light 16 and O-order light 17 not deflected by the elastic surface wave 18 emerge from the waveguide through a prism coupler 19.
Turning back to FIG. 1A, the deflected light 7 having emerged from the light deflector 1 is transmitted through the beam splitter 2 and is converged on the recording medium 6 on which information is recorded, by the objective lens 3. The signal light 8 reflected from the recording medium 6 while being subjected to modulation in accordance with the aforementioned information is separated from the deflected light 7 by the beam splitter 2 and is imaged on the light-receiving surface of the photodetector 5 by the condensing lens 4. The photodetector 5 detects the signal light 8 and reproduces the aforementioned information.
An information recording or reproducing apparatus using such a light deflector by diffraction has an excellent characteristic that high-speed scanning of the recording or reproducing light is possible. However, as shown in FIG. 1A, the apparatus according to the prior art is not provided with the focus control or tracking control function and therefore could not be intactly applied to an apparatus for effecting recording and/or reproduction of higher density, such as an optical disk apparatus or a magneto-optical disk apparatus.